1. Field of the Invention
This invention relates to an ion pump, and more particularly to an ion pump that is made to a simpler design using better-suited materials than conventional ion pumps.
2. Description of the Prior Art
FIG. 1 shows an example of conventional ion pumps, which comprises a magnet 1 and a stainless steel pump casing 2, with part 2a of the latter extending into the magnetic field generated by the former. The part 2a contains a stainless steel anode 3 and a titanium cathode 4.
As a result of Penning discharge, titanium atoms are spattered and stick to the internal surface of the pump casing 2. The active titanium atoms adsorb gas molecules in the pump casing 2.
With the gas in the pump casing 2 thus eliminated or evacuated, a given vessel (not shown) communicating with the pump casing 2 is also evacuated to establish a high degree of vacuum therein.
Made of stainless steel and titanium, conventional ion pumps must, in application of heat treatment, be kept at a high temperature not lower than 450.degree. C. for a long time (approximately 48 hours). Another problem is the extremely high cost of titanium cathodes.